A Family of Single-Isomer Chiral Resolving Agents for Capillary Electrophoresis. 2. Hepta-6-sulfato-β-cyclodextrin

A new, hydrophilic, single-isomer charged cyclodextrin, the sodium salt of hepta-6-sulfato-β-cyclodextrin has been synthesized, characterized, and used for the capillary electrophoretic separation of the enantiomers of numerous noncharged, acidic, basic, and zwitterionic analytes. Hepta-6-sulfato-β-cyclodextrin proved to be a much stronger complexing agent for all the analytes tested, in both low-pH and high-pH background electrolytes, than the previously synthesized, moderately hydrophobic heptakis(2,3-diacetyl-6-sulfato)-β-cyclodextrin. The separation selectivities of the two single-isomer, differently functionalized charged cyclodextrins often proved to be complementary. In agreement with the predictions of the charged resolving agent migration model, separation selectivity for the noncharged analytes decreased as the concentration of hepta-6-sulfato-β-cyclodextrin was increased. For acidic, basic, and zwitterionic analytes, selectivity could increase, decrease, or pass a maximum, depending on the binding strength of the enantiomers and ionic mobilities of both the complexed and noncomplexed forms of the enantiomers.